The present invention relates to a polymerization process for the production of a polyethylene. Preferably the polyethylene has a low level of extractables. Films produced from the polyethylene are characterized by having high strength properties.
Polyethylene polymers are well known and are useful in many applications. In particular, linear polyethylene polymers possess properties which distinguish them from other polyethylene polymers, such as branched ethylene homopolymers commonly referred to as LDPE (low density polyethylene). Certain of these properties are described by Anderson et al. U.S. Pat. No. 4,076,698.
A particularly useful polymerization medium for producing polyethylene polymers is a gas phase process. Examples of such are given in U.S. Pat. Nos. 3,709,853; 4,003,712; 4,011,382; 4,302,566; 4,543,399; 4,882,400; 5,352,749 and 5,541,270 and Canadian Patent No. 991,798 and Belgian Patent No. 839,380.
Ziegler-Natta type catalyst systems for the polymerization of olefins are well known in the art and have been known at least since the issuance of U.S. Pat. No. 3,113,115. Thereafter, many patents have been issued relating to new or improved Ziegler-Natta type catalysts. Exemplary of such patents are U.S. Pat. Nos. 3,594,330; 3,676,415; 3,644,318; 3,917,575; 4,105,847; 4,148,754; 4,256,866; 4,298,713; 4,311,752; 4,363,904; 4,481,301 and Reissue 33,683.
These patents disclose Ziegler-Natta type catalysts that are well known as typically consisting of a transition metal component and a co-catalyst that is typically an organoaluminum compound. Optionally used with the catalyst are activators such as halogenated hydrocarbons and activity modifiers such as electron donors.
The use of halogenated hydrocarbons with Ziegler-Natta type polymerization catalysts in the production of polyethylene is disclosed in U.S. Pat. No. 3,354,139 and European Patent Nos. EP 0 529 977 B1 and EP 0 703 246 A1. As disclosed, the halogenated hydrocarbons may reduce the rate of ethane formation, improve a catalyst efficiency, or provide other effects. Typical of such halogenated hydrocarbons are monohalogen and polyhalogen substituted saturated or unsaturated aliphatic, alicyclic, or aromatic hydrocarbons having 1 to 12 carbon atoms. Exemplary aliphatic compounds include methyl chloride, methyl bromide, methyl iodide, methylene chloride, methylene bromide, methylene iodide, chloroform, bromoform, iodoform, carbon tetrachloride, carbon tetrabromide, carbon tetraiodide, ethyl chloride, ethyl bromide, 1,2-dichloroethane, 1,2-dibromoethane, methylchloroform, perchloroethylene and the like. Exemplary alicyclic compounds include chlorocyclopropane, tetrachlorocyclopentane and the like. Exemplary aromatic compounds include chlorobenzene, hexabromobenzene, benzotrichloride and the like. These compounds may be used individually or as mixtures thereof.
It is also well known, in the polymerization of olefins, particularly where Ziegler-Natta type catalysts are employed, to utilize, optionally, electron donors. Such electron donors often aid in increasing the efficiency of the catalyst and/or in controlling the stereospecificity of the polymer when an olefin, other than ethylene, is polymerized. Electron donors, typically known as Lewis Bases, when employed during the catalyst preparation step are referred to as internal electron donors. Electron donors when utilized other than during the catalyst preparation step are referred to as external electron donors. For example, the external electron donor may be added to the preformed catalyst, to the prepolymer, and/or to the polymerization medium.
The use of electron donors in the field of propylene polymerization is well known and is primarily used to reduce the atactic form of the polymer and increase the production of the isotactic polymers. The use of electron donors generally improves the productivity of the catalyst in the production of isotactic polypropylene. This is shown generally in U.S. Pat. No. 4,981,930.
In the field of ethylene polymerization, where ethylene constitutes at least about 70% by weight of the total monomers present in the polymer, electron donors are utilized to control the molecular weight distribution (MWD) of the polymer and the activity of the catalyst in the polymerization medium. Exemplary patents describing the use of internal electron donors in producing linear polyethylene are U.S. Pat. Nos. 3,917,575; 4,187,385; 4,256,866; 4,293,673; 4,296,223; Reissue 33,683; U.S. Pat. Nos. 4,302,565; 4,302,566; and 5,470,812. The use of an external monoether electron donor, such as tetrahydrofuran (THF), to control molecular weight distribution is shown in U.S. Pat. No. 5,055,535; and the use of external electron donors to control the reactivity of catalyst particles is described in U.S. Pat. No. 5,410,002.
Illustrative examples of electron donors include carboxylic acids, carboxylic acid esters, alcohols, ethers, ketones, amines, amides, nitriles, aldehydes, thioethers, thioesters, carbonic esters, organosilicon compounds containing oxygen atoms, and phosphorus, arsenic or antimony compounds connected to an organic group through a carbon or oxygen atom.
The polymerization process of the present invention comprises the introduction into a polymerization medium containing ethylene and optionally other olefin(s), a Ziegler-Natta type polymerization catalyst, at least one halogenated hydrocarbon, at least one compound containing at least one carbon-oxygen-carbon linkage (Cxe2x80x94Oxe2x80x94C) of the formula R1xe2x80x94O(xe2x80x94R2xe2x80x94O)nxe2x80x94R3 where n ranges from 0 to 30, and R1, R2 and R3 independently contain from 1 to 30 carbon atoms and from 0 to 30 heteroatoms of an element, or mixtures thereof, selected from Groups 13, 14, 15, 16 and 17 of the Periodic Table of Elements, and further wherein R1, R2 and/or R3 can be linked and form part of a cyclic or polycyclic structure, as an external electron donor, and as a co-catalyst at least one compound of the formula,
XnER3-n,
wherein,
X is hydrogen, halogen, or mixtures of halogens, selected from fluorine, chlorine, bromine and iodine;
n ranges from 0 to 2;
E is an element from Group 13 of the Periodic Table of Elements such as boron, aluminum and gallium; and
R is a hydrocarbon group, containing from 1 to 100 carbon atoms and from 0 to 10 oxygen atoms, connected to the Group 13 element by a carbon or oxygen bond.
The external electron donor as defined herein, the co-catalyst defined herein, and the halogenated hydrocarbon may be added to the polymerization medium in any manner. The external electron donor as defined herein, the halogenated hydrocarbon, and/or the co-catalyst defined herein may be added to the catalyst just prior to addition to the polymerization medium, or added separately from the catalyst to the polymerization medium in any manner known in the art. For example, the external electron donor as defined herein may optionally be premixed with the co-catalyst prior to addition to the polymerization medium.
If a gas phase fluidized bed process is utilized for polymerization of the ethylene, it may be advantageous to add the external electron donor as defined herein prior to the heat removal means, e.g., the heat exchanger, to slow the rate of fouling of said heat removal means.
All mention herein to elements of Groups of the Periodic Table are made in reference to the Periodic Table of the Elements, as published in xe2x80x9cChemical and Engineering Newsxe2x80x9d, 63(5), 27, 1985. In this format, the Groups are numbered 1 to 18.
The present inventors have unexpectedly discovered that a particular combination of a Ziegler-Natta catalyst, at least one halogenated hydrocarbon, as a co-catalyst at least one compound of the formula,
XnER3-n,
wherein,
X is hydrogen, halogen, or mixtures of halogens, selected from fluorine, chlorine, bromine and iodine;
n ranges from 0 to 2;
E is an element from Group 13 of the Periodic Table of Elements such as boron, aluminum and gallium; and
R is a hydrocarbon group, containing from 1 to 100 carbon atoms and from 0 to 10 oxygen atoms, connected to the Group 13 element by a carbon or oxygen bond, and as an external electron donor, at least one compound containing at least one carbon-oxygen-carbon linkage (Cxe2x80x94Oxe2x80x94C) of the formula R1xe2x80x94O(xe2x80x94R2xe2x80x94O)nxe2x80x94R3 where n ranges from 0 to 30, and R1, R2 and R3 independently contain from 1 to 30 carbon atoms and from 0 to 30 heteroatoms of an element, or mixtures thereof, selected from Groups 13, 14, 15, 16 and 17 of the Periodic Table of Elements, and further wherein R1, R2 and/or R3 can be linked and form part of a cyclic or polycyclic structure, makes it possible to produce a polyethylene in an improved manner. Preferably the resultant polyethylene has a reduced level of extractables. Furthermore, films produced from these polyethylenes unexpectedly have high impact resistance as typified by Dart Impact values and have a good balance of machine direction (MD) and transverse direction (TD) tear values.
The compound used herein as external electron donor is any compound containing at least one carbon-oxygen-carbon linkage (Cxe2x80x94Oxe2x80x94C) of the formula R1xe2x80x94O(xe2x80x94R2xe2x80x94O)nxe2x80x94R3 where n ranges from 0 to 30, and R1, R2 and R3 independently contain from 1 to 30 carbon atoms and from 0 to 30 heteroatoms of an element, or mixtures thereof, selected from Groups 13, 14, 15, 16 and 17 of the Periodic Table of Elements, and further wherein R1, R2 and/or R3 can be linked and form part of a cyclic or polycyclic structure.
Exemplary of the R1, R2 and R3 groups suitable for use herein are C1-30 alkyl, C2-30 alkenyl, C4-30dienyl, C3-30 cycloalkyl, C3-30cycloalkenyl, C4-30cyclodienyl, C6-18aryl, C7-30aralkyl and C7-30alkaryl. Also exemplary are hydrocarbons containing from 1 to 30 carbon atoms and from 1 to 30 heteroatoms of an element, or mixtures thereof, from Groups 13, 14, 15, 16 and 17 of the Periodic Table of Elements such as, for example, B1-30borohydrocarbons, Si1-30silahydrocarbons, P1-30phosphahydrocarbons, S1-30 thiahydrocarbons, Cl1-30chlorohydrocarbons and halogenated hydrocarbons containing mixtures of halogens.
It is also suitable to utilize herein as the external electron donor, mixtures of compounds having the above formula.
Exemplary of compounds that may be used herein as external electron donors are compounds containing one Cxe2x80x94Oxe2x80x94C linkage where n=0, such as alkyl, alkenyl, dienyl and aryl substituted compounds of the formula R1xe2x80x94Oxe2x80x94R3. Specific examples are dimethyl ether; diethyl ether; dipropyl ether; diisopropyl ether; dibutyl ether; dipentyl ether; dihexyl ether; dioctyl ether; diisoamyl ether; di-tert-butyl ether; diphenyl ether; dibenzyl ether; divinyl ether; diallyl ether; dicyclopropyl ether; dicyclopentyl ether; dicyclohexyl ether; allyl methyl ether; allyl ethyl ether; allyl cyclohexyl ether; allyl phenyl ether; allyl benzyl ether; allyl 2-tolyl ether; allyl 3-tolyl ether; benzyl methyl ether; benzyl ethyl ether; benzyl isoamyl ether; benzyl chloromethyl ether; benzyl cyclohexyl ether; benzyl phenyl ether; benzyl 1-naphthyl ether; benzyl 2-naphthyl ether; butyl methyl ether; butyl ethyl ether; sec-butyl methyl ether; tert-butyl methyl ether; butyl cyclopentyl ether; butyl 2-chloroethyl ether; cyclopentyl methyl ether; cyclohexyl ethyl ether; cyclohexyl vinyl ether; tert-amyl methyl ether; sec-butyl ethyl ether; tert-butyl ethyl ether; tert-amyl ethyl ether; cyclododecyl methyl ether; bis(3-cyclopenten-1-yl) ether; 1-methoxy-1,3-cyclohexadiene; 1-methoxy-1,4-cyclohexadiene; chloromethyl methyl ether; chloromethyl ethyl ether; bis(2-tolyl) ether; trimethylsilylmethyl methyl ether; bis(trimethylsilylmethyl) ether; bis(2,2,2-trifluoroethyl) ether; benzyl 3-bromopropyl ether; benzyl 3-bromo-2-chloropropyl ether; dimethyl 2-methoxyethyl borate; dimethyl methoxymethyl borate; dimethoxy-2-methoxyethylborane; diphenyl-2-methoxyethylphosphine; diphenylmethoxymethylphosphine; 2-(2-thienyl)ethyl ethyl ether; 2-(2-thienyl)ethyl methyl ether; 2-(3-thienyl)ethyl ethyl ether; 2-(3-thienyl)ethyl methyl ether; 2-(2-methoxymethyl)-1,3,2-dioxaphospholane; 1-(2-methoxyethyl)pyrrole; 1-(2-methoxyethyl)pyrazole; 1-(2-methoxyethyl)imidazole; 2-(2-methoxyethyl)pyridine; bis(3-tolyl) ether; bis(1-naphthyl) ether; bis(2-naphthyl) ether; allyl 1-naphthyl ether; allyl 2-naphthyl ether; benzyl 2-tolyl ether; benzyl 3-tolyl ether; ethyl phenyl ether; ethyl 2-tolyl ether; ethyl 3-tolyl ether; ethyl 1-naphthyl ether; ethyl 2-naphthyl ether; methyl phenyl ether; methyl 2-tolyl ether; methyl 3-tolyl ether; methyl 1-naphthyl ether; methyl 2-naphthyl ether; 2-ethoxy-1-methylpyrrole; 3-methoxy-1-methylpyrrole; 2-ethoxythiophene; 3-methoxythiophene; 3-methoxy-1-methylpyrazole; 4-methoxy-1-methylpyrazole; 5-methoxy-1-methylpyrazole; 2-methoxy-1-methylimidazole; 4-methoxy-1-methylimidazole; 5-methoxy-1-methylimidazole; 3-methoxy-1-phenylpyrazole; 4-methoxy-1-phenylpyrazole; 5-methoxy-1-phenylpyrazole; 2-methoxy-1-phenylimidazole; 4-methoxy-1-phenylimidazole; 5-methoxy-1-phenylimidazole; 4-methoxy-1-methyl-1,2,3-triazole; 5-methoxy-1-methyl-1,2,3-triazole; 4-methoxy-1-phenyl-1,2,3-triazole; 5-methoxy-1-phenyl-1,2,3-triazole; 3-methoxy-1-methyl-1,2,4-triazole; 5-methoxy-1-methyl-1,2,4-triazole; 3-methoxy-1-phenyl-1,2,4-triazole; 5-methoxy-1-phenyl-1,2,4-triazole; 5-methoxy-1-methyltetrazole; 5-methoxy-1-phenyltetrazole; 3-methoxyisoxazole; 4-methoxyisoxazole; 5-methoxyisoxazole; 3-methoxy-1,2,4-oxadiazole; 5-methoxy-1,2,4-oxadiazole; 3-methoxyisothiazole; 4-methoxyisothiazole; 5-methoxyisothiazole; 2-methoxythiazole; 4-methoxythiazole; 5-methoxythiazole; 2-methoxypyridine; 3-methoxypyridine; 4-methoxypyridine; 3-methoxypyridazine; 4-methoxypyridazine; 2-methoxypyrimidine; 4-methoxypyrimidine; 5-methoxypyrimidine; 2-methoxypyrazine; 3-methoxy-1,2,4-triazine; 5-methoxy-1,2,4-triazine; 6-methoxy-1,2,4-triazine; 2-methoxy-1,3,5-triazine and the like. Also exemplary are C2-20cyclic compounds where R1 and R3 are linked and form part of a cyclic or polycyclic structure such as, for example, ethylene oxide; propylene oxide; 1,2-epoxybutane; cyclopentene oxide; epichlorohydrin; trimethylene oxide; 3,3-dimethyloxetane; furan; 2,3-dihydrofuran; 2,5-dihydrofuran; tetrahydrofuran; 2-methyltetrahydrofuran; 2,5-dimethyltetrahydrofuran; 4,5-dihydro-2-methylfuran; 2-methylfuran; 2,5-dimethylfuran; 3-bromofuran; 2,3-benzofuran; 2-methylbenzofuran; dibenzofuran; phthalan; xanthene; 1,2-pyran; 1,4-pyran; tetrahydropyran; 3-methyltetrahydropyran; 4-chlorotetrahydropyran; chroman; isochroman; oxocane; 2,3-epoxybutane; 1,2-epoxybut-3-ene; styrene oxide; 2-ethylfuran; 2-tert-butylfuran; 2,3-dimethylfuran; 2,3-dihydrobenzofuran; dimethyl 3-furylmethyl borate; 2-trimethylsilylfuran; 3-trimethylsilylfuran; oxazole; 1,3,4-oxadiazole; 3,4-dichloro-1,2-epoxybutane; 3,4-dibromo-1,2-epoxybutane and the like.
Exemplary compounds containing more than one Cxe2x80x94Oxe2x80x94C linkage include alkyl, alkenyl, dienyl and aryl substituted compounds of the formula R1xe2x80x94O(xe2x80x94R2xe2x80x94O)nxe2x80x94R3 where n ranges from 1 to 30. Specific examples are, dimethoxymethane; 1,1-dimethoxyethane; 1,1,1-trimethoxyethane; 1,1,2-trimethoxyethane; 1,1-dimethoxypropane; 1,2-dimethoxypropane; 2,2-dimethoxypropane; 1,3-dimethoxypropane; 1,1,3-trimethoxypropane; 1,4-dimethoxybutane; 1,2-dimethoxybenzene; 1,3-dimethoxybenzene; 1,4-dimethoxybenzene; ethylene glycol dimethyl ether; ethylene glycol diethyl ether; ethylene glycol divinyl ether; ethylene glycol diphenyl ether; ethylene glycol tert-butyl methyl ether; ethylene glycol tert-butyl ethyl ether; di(ethylene glycol) dimethyl ether; di(ethylene glycol) diethyl ether; di(ethylene glycol) dibutyl ether; di(ethylene glycol) tert-butyl methyl ether; tri(ethylene glycol) dimethyl ether; tri(ethylene glycol) diethyl ether; tetra(ethylene glycol) dimethyl ether; tetra(ethylene glycol) diethyl ether; ethylene glycol bis(trimethylsilylmethyl) ether; di(ethylene glycol) methyl trimethylsilyl ether; tris(2-methoxyethyl) borate; ethylene glycol chloromethyl bromomethyl ether; 2-(2-ethylhexyl)-1,3-dimethoxypropane; 2-isopropyl-1,3-dimethoxypropane; 2-butyl-1,3-dimethoxypropane; 2-sec-butyl-1,3-dimethoxypropane; 2-tert-butyl-1,3-dimethoxypropane; 2-cyclohexyl-1,3-dimethoxypropane; 2-phenyl-1,3-dimethoxypropane; 2-cumyl-1,3-dimethoxypropane; 2-(2-phenylethyl)-1,3-dimethoxypropane; 2-(2-cyclohexylethyl)-1,3-dimethoxypropane; 2-(p-chlorophenyl)-1,3-dimethoxypropane; 2-(p-fluorophenyl)-1,3-dimethoxypropane; 2-(diphenylmethyl)-1,3-dimethoxypropane; 2,2-dicyclohexyl-1,3-dimethoxypropane; 2,2-diethyl-1,3-dimethoxypropane; 2,2-dipropyl-1,3-dimethoxypropane; 2,2-diisopropyl-1,3-dimethoxypropane; 2,2-dibutyl-1,3-dimethoxypropane; 2,2-diisobutyl-1,3-dimethoxypropane; 2-methyl-2-ethyl-1,3-dimethoxypropane; 2-methyl-2-propyl-1,3-dimethoxypropane; 2-methyl-2-butyl-1,3-dimethoxypropane; 2-methyl-2-benzyl-1,3-dimethoxypropane; 2-methyl-2-methylcyclohexyl-1,3-dimethoxypropane; 2-isopropyl-2-isopentyl-1,3-dimethoxypropane; 2,2-bis(2-cyclohexylmethyl)-1,3-dimethoxypropane and the like. Also exemplary are C3-20cyclic compounds where R1, R2 and/or R3 are linked and form part of a cyclic or polycyclic structure. Specific examples are 2,5-dimethoxyfuran; 2-methoxyfuran; 3-methoxyfuran; 2-methoxytetrahydropyran; 3-methoxytetrahydropyran; 1,3-dioxolane; 2-methyl-1,3-dioxolane; 2,2-dimethyl-1,3-dioxolane; 2-ethyl-2-methyl-1,3-dioxolane; 2,2-tetramethylene-1,3-dioxolane; 2,2-pentamethylene-1,3-dioxolane; 2-vinyl-1,3-dioxolane; 2-chloromethyl-1,3-dioxolane; 2-methoxy-1,3-dioxolane; 1,4-dioxaspiro[4,4]non-6-ene; 1,4,9,12-tetraoxadispiro(4,2,4,2)tetradecane; 1,3-dioxane; 1,4-dioxane; 4-methyl-1,3-dioxane; 1,3,5-trioxane; 2,4,8,10-tetraoxaspiro(5,5)undecane; 12-crown-4; 15-crown-5; cis-4,7-dihydro-1,3-dioxepin; 1,7-dioxaspiro(5,5)undecane; 3,4-epoxytetrahydrofuran; 2,2-dimethyl-4-vinyl-1,3-dioxolane; tri-2-furylphosphine; 2-trimethylsilyl-1,3-dioxolane; 2-(3-thienyl)-1,3-dioxolane; 2-bromochloromethyl-1,3-dioxolane; 2-methoxyoxazole; 4-methoxyoxazole; 5-methoxyoxazole; 2-methoxy-1,3,4-oxadiazole and the like.
Preferred for use herein as external electron donors are dimethyl ether; diethyl ether; dipropyl ether; diisopropyl ether; dibutyl ether; diisoamyl ether; di-tert-butyl ether; diphenyl ether; dibenzyl ether; divinyl ether; butyl methyl ether; butyl ethyl ether; sec-butyl methyl ether; tert-butyl methyl ether; cyclopentyl methyl ether; cyclohexyl ethyl ether; tert-amyl methyl ether; sec-butyl ethyl ether; chloromethyl methyl ether; trimethylsilylmethyl methyl ether; bis(trimethylsilylmethyl) ether; bis(2,2,2-trifluoroethyl) ether; methyl phenyl ether; ethylene oxide; propylene oxide; 1,2-epoxybutane; cyclopentene oxide; epichlorohydrin; furan; 2,3-dihydrofuran; 2,5-dihydrofuran; tetrahydrofuran; 2-methyltetrahydrofuran; 2,5-dimethyltetrahydrofuran; 2-methylfuran; 2,5-dimethylfuran; tetrahydropyran; 1,2-epoxybut-3-ene; styrene oxide; 2-ethylfuran; oxazole; 1,3,4-oxadiazole; 3,4-dichloro-1,2-epoxybutane; 3,4-dibromo-1,2-epoxybutane; dimethoxymethane; 1,1-dimethoxyethane; 1,1,1-trimethoxymethane; 1,1,1-trimethoxyethane; 1,1,2-trimethoxyethane; 1,1-dimethoxypropane; 1,2-dimethoxypropane; 2,2-dimethoxypropane; 1,3-dimethoxypropane; 1,1,3-trimethoxypropane; 1,4-dimethoxybutane; 1,2-dimethoxybenzene; 1,3-dimethoxybenzene; 1,4-dimethoxybenzene; ethylene glycol dimethyl ether; di(ethylene glycol) dimethyl ether; di(ethylene glycol) diethyl ether; di(ethylene glycol) dibutyl ether; di(ethylene glycol) tert-butyl methyl ether; tri(ethylene glycol) dimethyl ether; tri(ethylene glycol) diethyl ether; tetra(ethylene glycol) dimethyl ether; 2,2-diethyl-1,3-dimethoxypropane; 2-methyl-2-ethyl-1,3-dimethoxypropane; 2-methoxyfuran; 3-methoxyfuran; 1,3-dioxolane; 2-methyl-1,3-dioxolane; 2,2-dimethyl-1,3-dioxolane; 2-ethyl-2-methyl-1,3-dioxolane; 2,2-tetramethylene-1,3-dioxolane; 2,2-pentamethylene-1,3-dioxolane; 1,3-dioxane; 1,4-dioxane; 4-methyl-1,3-dioxane; 1,3,5-trioxane and 3,4-epoxytetrahydrofuran.
Most preferred for use herein as the external electron donor are tetrahydrofuran, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dioctyl ether, tert-butyl methyl ether, trimethylene oxide and tetrahydropyran.
The co-catalyst used in the process of the present invention is at least one compound of the formula,
XnER3-n,
wherein,
X is hydrogen, halogen, or mixtures of halogens, selected from fluorine, chlorine, bromine and iodine;
n ranges from 0 to 2;
E is an element from Group 13 of the Periodic Table of Elements such as boron, aluminum and gallium; and
R is a hydrocarbon group, containing from 1 to 100 carbon atoms and from 0 to 10 oxygen atoms, connected to the Group 13 element by a carbon or oxygen bond.
Exemplary of the R group suitable for use herein is C1-100alkyl, C1-100alkoxy, C2-100alkenyl, C2-100dienyl, C3-100cycloalkyl, C3-100cycloalkoxy, C3-100cycloalkenyl, C4-100cyclodienyl, C6-100aryl, C7-100aralkyl, C7-100aralkoxy and C7-100alkaryl. Also exemplary of the R group are hydrocarbons containing from 1 to 100 carbon atoms and from 1 to 10 oxygen atoms.
Exemplary of the co-catalyst compounds used in the process of the present invention where n=0 are trimethylaluminum; triethylborane; triethylgallane; triethylaluminum; tri-n-propylaluminum; tri-n-butylaluminum; tri-n-pentylaluminum; triisoprenylaluminum; tri-n-hexylaluminum; tri-n-heptylaluminum; tri-n-ocytlaluminum; triisopropylaluminum; triisobutylaluminum; tris(cylcohexylmethyl)aluminum; dimethylaluminum methoxide; dimethyaluminum ethoxide; diethylaluminum ethoxide and the like. Exemplary of compounds where n=1 are dimethylaluminum chloride; diethylaluminum chloride; di-n-propylaluminum chloride; di-n-butylaluminum chloride; di-n-pentylaluminum chloride; diisoprenylaluminum chloride; di-n-hexylaluminum chloride; di-n-heptylaluminum chloride; di-n-octylaluminum chloride; diisopropylaluminum chloride; diisobutylaluminum chloride; bis(cyclohexylmethyl)aluminum chloride; diethylaluminum fluoride; diethylaluminum bromide; diethylaluminum iodide; dimethylaluminum hydride; diethylaluminum hydride; di-n-propylaluminum hydride; di-n-butylaluminum hydride; di-n-pentylaluminum hydride; diisoprenylaluminum hydride; di-n-hexylaluminum hydride; di-n-heptylaluminum hydride; di-n-octylaluminum hydride; diisopropylaluminum hydride; diisobutylaluminum hydride; bis(cyclohexylmethyl)aluminum hydride; chloromethylaluminum methoxide; chloromethylaluminum ethoxide; chloroethylaluminum ethoxide and the like. Exemplary of compounds where n=2 are methylaluminum dichloride; ethylaluminum dichloride; n-propylaluminum dichloride; n-butylaluminum dichloride; n-pentylaluminum dichloride; isoprenylaluminum dichloride; n-hexylaluminum dichloride; n-heptylaluminum dichloride; n-octylaluminum dichloride; isopropylaluminum dichloride; isobutylaluminum dichloride; (cylcohexylmethyl)aluminum dichloride and the like. Also exemplary are alkylaluminum sesquialkoxides such as methylaluminum sesquimethoxide; ethylaluminum sesquiethoxide; n-butylaluminum sesqui-n-butoxide and the like. Also exemplary are alkylaluminum sesquihalides such as methylaluminum sesquichloride; ethylaluminum sesquichloride; isobutylaluminum sesquichloride; ethylaluminum sesquifluoride; ethylaluminum sesquibromide; ethylaluminum sesquiiodide and the like.
Preferred for use herein as co-catalysts are trialkylaluminums such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, tri-2-methylpentylaluminum, tri-n-octylaluminum, tri-n-decylaluminum; and dialkylaluminum halides such as dimethylaluminum chloride, diethylaluminum chloride, dibutylaluminum chloride, diisobutylaluminum chloride, diethylaluminum bromide and diethylaluminum iodide; and alkylaluminum sesquihalides such as methylaluminum sesquichloride, ethylaluminum sesquichloride, n-butylaluminum sesquichloride, isobutylaluminum sesquichloride, ethylaluminum sesquifluoride, ethylaluminum sesquibromide and ethylaluminum sesquiiodide.
Most preferred for use herein as co-catalysts are trialkylaluminums such as trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, tri-2-methylpentylaluminum, tri-n-octylaluminum and dialkylaluminum halides such as dimethylaluminum chloride, diethylaluminum chloride, dibutylaluminum chloride, diisobutylaluminum chloride and alkylaluminum sesquihalides such as methylaluminum sesquichloride, ethylaluminum sesquichloride, n-butylaluminum sesquichloride and isobutylaluminum sesquichloride.
Mixtures of compounds of the above formula XnER3-n, also can be utilized herein as the co-catalyst.
Any halogenated hydrocarbon may be used in the process of the present invention. If desired more than one halogenated hydrocarbon can be used. Typical of such halogenated hydrocarbons are monohalogen and polyhalogen substituted saturated or unsaturated aliphatic, alicyclic, or aromatic hydrocarbons having 1 to 12 carbon atoms. Exemplary aliphatic compounds are fluoromethane; chloromethane; bromomethane; iodomethane; difluromethane; dichloromethane; dibromomethane; diiodomethane; chloroform; bromoform; iodoform; carbon tetrachloride; carbon tetrabromide; carbon tetraiodide; bromofluoromethane; bromochloromethane; bromoiodomethane; chlorofluoromethane; chloroiodomethane; fluoroiodomethane; bromodifluromethane; bromodichloromethane; bromodiiodomethane; chlorodifluromethane; chlorodibromomethane; chlorodiiodomethane; fluorodichloromethane; fluorodibromomethane; fluorodiiodomethane; iododifluromethane; iododichloromethane; iododibromomethane; bromotrifluoromethane; bromotrichloromethane; bromotriiodomethane; chlorotrifluoromethane; chlorotribromomethane; chlorotriiodomethane; fluorotrichloromethane; fluorotribromomethane; fluorotriiodomethane; iodotrifluoromethane; iodotrichloromethane; iodotribromomethane; fluoroethane; chloroethane; bromoethane; iodoethane; 1,1-difluoroethane; 1,1-dichloroethane; 1,1-dibromoethane; 1,1-diiodoethane; 1,2-difluoroethane; 1,2-dichloroethane; 1,2-dibromoethane; 1,2-diiodoethane; 1-bromo-1-fluoroethane; 1-bromo-1-chloroethane; 1-bromo-1-iodoethane; 1-chloro-1-fluoroethane; 1-chloro-1-iodoethane; 1-fluoro-1-iodoethane; 1-bromo-2-fluoroethane; 1-bromo-2-chloroethane; 1-bromo-2-iodoethane; 1-chloro-2-fluoroethane; 1-chloro-2-iodoethane; 1-fluoro-2-iodoethane; 1,1,1-trifluoroethane; 1,1,1-trichloroethane; 1,1,1-tribromoethane; 1,1,1-triiodoethane; 1,1,2-trifluoroethane; 1,1,2-trichloroethane; 1,1,2-tribromoethane; 1,1,2-triiodoethane; 1-bromo-1,1-difluoroethane; 1-bromo-1,1-dichloroethane; 1-bromo-1,1-diiodoethane; 1-chloro-1,1-difluoroethane; 1-chloro-1,1-dibromoethane; 1-chloro-1,1-diiodoethane; 1-fluoro-1,1-dichloroethane; 1-fluoro-1,1-dibromoethane; 1-fluoro-1,1-diiodoethane; 1-iodo-1,1-difluoroethane; 1-iodo-1,1-dichloroethane; 1-iodo-1,1-dibromoethane; 1-bromo-1,2-difluoroethane; 1-bromo-1,2-dichloroethane; 1-bromo-1,2-diiodoethane; 1-chloro-1,2-difluoroethane; 1-chloro-1,2-dibromoethane; 1-chloro-1,2-diiodoethane; 1-fluoro-1,2-dichloroethane; 1-fluoro-1,2-dibromoethane; 1-fluoro-1,2-diiodoethane; 1-iodo-1,2-difluoroethane; 1-iodo-1,2-dichloroethane; 1-iodo-1,2-dibromoethane; 2-bromo-1,1-difluoroethane; 2-bromo-1,1-dichloroethane; 2-bromo-1,1-diiodoethane; 2-chloro-1,1-difluoroethane; 2-chloro-1,1-dibromoethane; 2-chloro-1,1-diiodoethane; 2-fluoro-1,1-dichloroethane; 2-fluoro-1,1-dibromoethane; 2-fluoro-1,1-diiodoethane; 2-iodo-1,1-difluoroethane; 2-iodo-1,1-dichloroethane; 2-iodo-1,1-dibromoethane; 1,1,1,2-tetrafluoroethane; 1,1,1,2-tetrachloroethane; 1,1,1,2-tetrabromoethane; 1,1,1,2-tetraiodoethane; 1,1,2,2-tetrafluoroethane; 1,1,2,2-tetrachloroethane; 1,1,2,2-tetrabromoethane; 1,1,2,2-tetraiodoethane; 2-bromo-1,1,1-trifluoroethane; 2-bromo-1,1,1-trichloroethane; 2-bromo-1,1,1-triiodoethane; 2-chloro-1,1,1-trifluoroethane; 2-chloro-1,1,1-tribromoethane; 2-chloro-1,1,1-triiodoethane; 2-fluoro-1,1,1-trichloroethane; 2-fluoro-1,1,1-tribromoethane; 2-fluoro-1,1,1-triiodoethane; 2-iodo-1,1,1-trifluoroethane; 2-iodo-1,1,1-trichloroethane; 2-iodo-1,1,1-tribromoethane; 1,1-dibromo-2,2-difluoroethane; 1,1-dibromo-2,2-dichloroethane; 1,1-dibromo-2,2-diiodoethane; 1,1-dichloro-2,2-difluoroethane; 1,1-dichloro-2,2-diiodoethane; 1,1-difluoro-2,2-diiodoethane; 1,2-dibromo-1,2-difluoroethane; 1,2-dibromo-1,2-dichloroethane; 1,2-dibromo-1,2-diiodoethane; 1,2-dichloro-1,2-difluoroethane; 1,2-dichloro-1,2-diiodoethane; 1,2-difluoro-1,2-diiodoethane; 2-bromo-2-chloro-1,1,1-trifluoroethane; hexafluoroethane; hexachloroethane; chloropentafluoroethane; iodopentafluoroethane; 1,2-dibromotetrachloroethane; fluoroethylene; chloroethylene; bromoethylene; iodoethylene; 1,1-difluorothylene; 1,1-dichloroethylene; 1,1-dibromoethylene; 1,1-diiodoethylene; 1,1,2-trifluorothylene; 1,1,2-trichloroethylene; 1,1,2-tribromoethylene; 1,1,2-triiodoethylene; 1,1,2,2-tetrafluorothylene; 1,1,2,2-tetrachloroethylene; 1,1,2,2-tetrabromoethylene; 1,1,2,2-tetraiodoethylene; 1-bromo-1,2,2-trifluorothylene; 1-bromo-1,2,2-trichloroethylene; 1-bromo-1,2,2-triiodoethylene; 1-chloro-1,2,2-trifluorothylene; 1-chloro-1,2,2-tribromoethylene; 1-chloro-1,2,2-triiodoethylene; 1-fluoro-1,2,2-trichloroethylene; 1-fluoro-1,2,2-tribromoethylene; 1-fluoro-1,2,2-triiodoethylene; 1-iodo-1,2,2-trifluorothylene, 1-iodo-1,2,2-trichloroethylene; 1-iodo-1,2,2-tribromoethylene; 1,1-dibromo-2,2-difluorothylene; 1,1-dibromo-2,2-dichloroethylene; 1,1-dibromo-2,2-diiodoethylene; 1,1-dichloro-2,2-difluoroethylene; 1,1-dichloro-2,2-diiodoethylene; 1,1-difluoro-2,2-diiodoethylene; 1,2-dibromo-1,2-difluorothylene; 1,2-dibromo-1,2-dichloroethylene; 1,2-dibromo-1,2-diiodoethylene; 1,2-dichloro-1,2-difluoroethylene; 1,2-dichloro-1,2-diiodoethylene; 1,2-difluoro-1,2-diiodoethylene; 1-fluoropropane; 1-bromopropane; 1-chloropropane; 1-iodopropane; 2-fluoropropane; 2-bromopropane; 2-chloropropane; 2-iodopropane; 1,3-difluoropropane; 1,3-dibromopropane; 1,3-dichloropropane; 1,3-diiodopropane; 1-fluorobutane; 1-bromobutane; 1-chlorobutane; 1-iodobutane; 2-fluorobutane; 2-bromobutane; 2-chlorobutane; 2-iodobutane; 1-fluoro-2-methylpropane; 1-bromo-2-methylpropane; 1-chloro-2-methylpropane; 1-iodo-2-methylpropane; 2-fluoro-2-methylpropane; 2-bromo-2-methylpropane; 2-chloro-2-methylpropane; 2-iodo-2-methylpropane; 1-fluoropentane; 1-bromopentane; 1-chloropentane; 1-iodopentane; 2-fluoropentane; 2-bromopentane; 2-chloropentane; 2-iodopentane; 3-fluoropentane; 3-bromopentane; 3-chloropentane; 3-iodopentane; 1-fluoro-2-methyl-butane; 1-bromo-2-methyl-butane; 1chloro-2-methyl-butane; 1-iodo-2-methyl-butane; 1-fluoro-3-methyl-butane; 1-bromo-3-methyl-butane; 1-chloro-3-methyl-butane; 1-iodo-3-methyl-butane; 2-fluoro-2-methyl-butane; 2-bromo-2-methyl-butane; 2-chloro-2-methyl-butane; 2-iodo-2-methyl-butane; 1-fluoro-2,2-dimethylpropane; 1-bromo-2,2-dimethylpropane; 1-chloro-2,2-dimethylpropane; 1-iodo-2,2-dimethylpropane; hexafluoropropene; hexachloropropene; perfluoro-2-methyl-2-pentene; perfluoropropyl chloride; perfluoroisopropyl chloride; perfluoropropyl iodide; perfluoroisopropyl iodide; 1,2-dibromohexafluoropropane; perfluoropentane; perfluorohexane and the like.
Exemplary alicyclic compounds are chlorocyclopropane, hexachlorocyclopentadiene, pentachlorocyclopropane; chlorocyclobutane; chlorocyclopentane; chlorocyclohexane; 1,1-dichlorocyclobutane; 1,1-dichlorocyclopentane; 1,1-dichlorocyclohexane; cis-1,2-dichlorocyclobutane; cis-1,2-dichlorocyclopentane; cis-1,2-dichlorocyclohexane; trans-1,2-dichlorocyclobutane; trans-1,2-dichlorocyclopentane, trans-1,2-dichlorocyclohexane; alpha-1,2,3,4,5,6-hexachlorocyclohexane; tetrachlorocyclopropene and the like.
Exemplary aromatic compounds are fluorobenzene; chlorobenzene; bromobenzene; iodobenzene; 1,2-difluorobenzene; 1,2-dichlorobenzene; 1,2-dibromobenzene; 1,2-diidobenzene; 1,3-difluorobenzene; 1,3-dichlorobenzene; 1,3-dibromobenzene; 1,3-diiodobenzene; 1,4-difluorobenzene; 1,4-dichlorobenzene; 1,4-dibromobenzene; 1,4-diiodobenzene; 1-bromo-2-fluorobenzene; 1-bromo-2-chlorobenzene; 1-bromo-2-iodobenzene; 1-chloro-2-fluorobenzene; 1-chloro-2-iodobenzene; 1-fluoro-2-iodobenzene; 1-bromo-3-fluorobenzene; 1-bromo-3-chlorobenzene; 1-bromo-3-iodobenzene; 1-chloro-3-fluorobenzene; 1-chloro-3-iodobenzene; 1-fluoro-3-iodobenzene; 1-bromo-4-fluorobenzene; 1-bromo-4-chlorobenzene; 1-bromo-4-iodobenzene; 1-chloro-4-fluorobenzene; 1-chloro-4-iodobenzene; 1-fluoro-4-iodobenzene; 1,2,3-trifluorobenzene; 1,2,3-trichlorobenzene; 1,2,3-tribromobenzene; 1,2,3-triiodobenzene; 1,2,4-trifluorobenzene; 1,2,4-trichlorobenzene; 1,2,4-tribromobenzene; 1,2,4-triiodobenzene; 1,2,3,4-tetrafluorobenzene; 1,2,3,4-tetrachlorobenzene; 1,2,3,4-tetrabromobenzene; 1,2,3,4-tetraiodobenzene; 1,2,3,5-tetrafluorobenzene; 1,2,3,5-tetrachlorobenzene; 1,2,3,5-tetrabromobenzene; 1,2,3,5-tetraiodobenzene; pentafluorobenzene; pentachlorobenzene; pentabromobenzene; pentaiodobenzene; hexafluorobenzene; hexachlorobenzene; hexabromobenzene; hexaiodobenzene; benzyl bromide; benzyl chloride; benzyl fluoride; benzyl iodide; alpha,alpha-dibromotoluene; alpha,alpha-dichlorotoluene; alpha,alpha-difluorotoluene; alpha,alpha-diiodotoluene; benzotribromide; benzotrichloride; benzotrifluoride; benzotriiodide; 2-bromotoluene; 2-chlorotoluene; 2-fluorotoluene; 2-iodotoluene; 3-bromotoluene; 3-chlorotoluene; 3-fluorotoluene; 3-iodotoluene; 4-bromotoluene; 4-chlorotoluene; 4-fluorotoluene; 4-iodotoluene; 2-bromobenzyl bromide; 2-chlorobenzyl bromide; 2-fluorobenzyl bromide; 2-iodobenzyl bromide; 2-bromobenzyl chloride; 2-chlorobenzyl chloride; 2-fluorobenzyl chloride; 2-iodobenzyl chloride; 2-bromobenzyl fluoride; 2-chlorobenzyl fluoride; 2-fluorobenzyl fluoride; 2-iodobenzyl fluoride; 2-bromobenzyl iodide; 2-chlorobenzyl iodide; 2-fluorobenzyl iodide; 2-iodobenzyl iodide; 3-bromobenzyl bromide; 3-chlorobenzyl bromide; 3-fluorobenzyl bromide; 3-iodobenzyl bromide; 3-bromobenzyl chloride; 3-chlorobenzyl chloride; 3-fluorobenzyl chloride; 3-iodobenzyl chloride; 3-bromobenzyl fluoride; 3-chlorobenzyl fluoride; 3-fluorobenzyl fluoride; 3-iodobenzyl fluoride; 3-bromobenzyl iodide; 3-chlorobenzyl iodide; 3-fluorobenzyl iodide; 3-iodobenzyl iodide; 4-bromobenzyl bromide; 4-chlorobenzyl bromide; 4-fluorobenzyl bromide; 4-iodobenzyl bromide; 4-bromobenzyl chloride; 4-chlorobenzyl chloride; 4-fluorobenzyl chloride; 4-iodobenzyl chloride; 4-bromobenzyl fluoride; 4-chlorobenzyl fluoride; 4-fluorobenzyl fluoride; 4-iodobenzyl fluoride; 4-bromobenzyl iodide; 4-chlorobenzyl iodide; 4-fluorobenzyl iodide; 4-iodobenzyl iodide and the like.
Preferred for use in the process of the present invention are dichloromethane; dibromomethane; chloroform; carbon tetrachloride; bromochloromethane; chlorofluoromethane; bromodichloromethane; chlorodifluoromethane; fluorodichloromethane; chlorotrifluoromethane; fluorotrichloromethane; 1,2-dichloroethane; 1,2-dibromoethane; 1-chloro-1-fluoroethane; 1-chloro-1,1-difluoroethane; 1-chloro-1,2-difluoroethane; 2-chloro-1,1-difluoroethane; 1,1,1,2-tetrafluoroethane; 1,1,1,2-tetrachloroethane; 2-chloro-1,1,1-trifluoroethane; 1,1-dichloro-2,2-difluoroethane; 1,2-dichloro-1,2-difluoroethane; hexafluoroethane; hexachloroethane; chloropentafluoroethane; 1,2-dibromotetrachloroethane; 1,1,2,2-tetrachloroethylene; 1-chloro-1,2,2-trifluorothylene; 1-fluoro-1,2,2-trichloroethylene; hexafluoropropene; hexachlorocyclopentadiene and hexachloropropene.
Most preferred for use in the process of the present invention are dichloromethane; chloroform; carbon tetrachloride; chlorofluoromethane; chlorodifluromethane; dichlorodifluoromethane;, fluorodichloromethane; chlorotrifluoromethane; fluorotrichloromethane; 1,2-dichloroethane; 1,2-dibromoethane; 1,1,1,2-tetrachloroethane; 2-chloro-1,1,1-trifluoroethane; 1,1-dichloro-2,2-difluoroethane; 1,2-dichloro-1,2-difluoroethane; hexafluoroethane; hexachloroethane; hexafluoropropene; hexachlorocyclopentadiene and hexachloropropene.
The halogenated hydrocarbons may be used individually or as mixtures thereof.
The polymerization process of the present invention may be carried out using any suitable process. For example, there may be utilized polymerization in suspension, in solution, in super-critical or in the gas phase media. All of these polymerization processes are well known in the art.
A particularly desirable method for producing polyethylene polymers according to the present invention is a gas phase polymerization process preferably utilizing a fluidized bed reactor. This type reactor and means for operating the reactor are well known and completely described in U.S. Pat. Nos. 3,709,853; 4,003,712; 4,011,382; 4,012,573; 4,302,566; 4,543,399; 4,882,400; 5,352,749; 5,541,270; Canadian Patent No. 991,798 and Belgian Patent No. 839,380. These patents disclose gas phase polymerization processes wherein the polymerization medium is either mechanically agitated or fluidized by the continuous flow of the gaseous monomer and diluent. The entire contents of these patents are incorporated herein by reference.
In general, the polymerization process of the present invention may be effected as a continuous gas phase process such as a fluid bed process. A fluid bed reactor for use in the process of the present invention typically comprises a reaction zone and a so-called velocity reduction zone. The reaction zone comprises a bed of growing polymer particles, formed polymer particles and a minor amount of catalyst particles fluidized by the continuous flow of the gaseous monomer and diluent to remove heat of polymerization through the reaction zone. Optionally, some of the recirculated gases may be cooled and compressed to form liquids that increase the heat removal capacity of the circulating gas stream when readmitted to the reaction zone. A suitable rate of gas flow may be readily determined by simple experiment. Make up of gaseous monomer to the circulating gas stream is at a rate equal to the rate at which particulate polymer product and monomer associated therewith is withdrawn from the reactor and the composition of the gas passing through the reactor is adjusted to maintain an essentially steady state gaseous composition within the reaction zone. The gas leaving the reaction zone is passed to the velocity reduction zone where entrained particles are removed. Finer entrained particles and dust may be removed in a cyclone and/or fine filter. The gas is passed through a heat exchanger wherein the heat of polymerization is removed, compressed in a compressor and then returned to the reaction zone.
In more detail, the reactor temperature of the fluid bed process herein ranges from about 30xc2x0 C. to about 110xc2x0 C. In general, the reactor temperature is operated at the highest temperature that is feasible taking into account the sintering temperature of the polymer product within the reactor.
The process of the present invention is suitable for the production of homopolymers of ethylene and/or copolymers, terpolymers, and the like, of ethylene and at least one or more other olefins. Preferably the olefins are alpha-olefins. The olefins, for example, may contain from 3 to 16 carbon atoms. Particularly preferred for preparation herein by the process of the present invention are linear polyethylenes. Such linear polyethylenes are preferably linear homopolymers of ethylene and linear copolymers of ethylene and at least one alpha-olefin wherein the ethylene content is at least about 70% by weight of the total monomers involved. Exemplary alpha-olefins that may be utilized herein are propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methylpent-1-ene, 1-decene, 1-dodecene, 1-hexadecene and the like. Also utilizable herein are polyenes such as 1,3-hexadiene, 1,4-hexadiene, cyclopentadiene, dicyclopentadiene, 4-vinylcyclohex-1-ene, 1,5-cyclooctadiene, 5-vinylidene-2-norbornene and 5-vinyl-2-norbornene, and olefins formed in situ in the polymerization medium. When olefins are formed in situ in the polymerization medium, the formation of linear polyethylenes containing long chain branching may occur.
The polymerization reaction of the present invention is carried out in the presence of a Ziegler-Natta type catalyst. In the process of the invention, the catalyst can be introduced in any manner known in the art. For example, the catalyst can be introduced directly into the polymerization medium in the form of a solution, a slurry or a dry free flowing powder. The catalyst can also be used in the form of a deactivated catalyst, or in the form of a prepolymer obtained by contacting the catalyst with one or more olefins in the presence of a co-catalyst.
The Ziegler-Natta catalysts are well known in the industry. The Ziegler-Natta catalysts in the simplest form are comprised of a transition metal compound and an organometallic co-catalyst compound. The method of the transition metal compound is a metal of Groups 4, 5, 6, 7, 8, 9 and 10 of the Periodic Table of the Elements, as published in xe2x80x9cChemical and Engineering Newsxe2x80x9d, 63(5), 27, 1985. In this format, the groups are numbered 1-18. Exemplary of such transition metals are titanium, zirconium, vanadium, chromium, manganese, iron, cobalt, nickel, and the like, and mixtures thereof. In a preferred embodiment the transition metal is selected from the group consisting of titanium, zirconium, vanadium and chromium, and in a still further preferred embodiment, the transition metal is titanium. The Ziegler-Natta catalyst can optionally contain magnesium and chlorine. Such magnesium and chlorine containing catalysts may be prepared by any manner known in the art.
In the event that a prepolymerized form of the catalyst is to be employed then the organometallic co-catalyst compound used to form the prepolymer can be any organometallic compound containing a metal of Groups 1, 2, 11, 12, 13 and 14 of the above described Periodic Table of the Elements. Exemplary of such metals are lithium, magnesium, copper, zinc, boron, silicon and the like. However, when a prepolymer is employed, a co-catalyst of the above formula XnER3-n is still utilized as the co-catalyst in the polymerization medium. The external electron donor and/or the halogenated hydrocarbon can, if desired, be added to the prepolymer.
The catalyst system may contain conventional components in addition to the transition metal component, the external electron donor defined herein, the halogenated hydrocarbon and the co-catalyst component. For example, there may be added any magnesium compound known in the art.
The Ziegler-Natta catalyst may be prepared by any method known in the art. The catalyst can be in the form of a solution, a slurry or a dry free flowing powder. The amount of Ziegler-Natta catalyst used is that which is sufficient to allow production of the desired amount of the polyethylene.
In carrying out the polymerization process of the present invention, the co-catalyst is added to the polymerization medium in any amount sufficient to effect production of the desired polyethylene. It is preferred to utilized the co-catalyst in a molar ratio of co-catalyst to transition metal component of the Ziegler-Natta catalyst ranging from about 1:1 to about 100:1. In a more preferred embodiment, the molar ratio of co-catalyst to transition metal component ranges from about 1:1 to about 50:1.
In carrying out the polymerization process of the present invention the external electron donor is added in any manner. For example, the external electron donor may be added to the preformed catalyst, to the prepolymer during the prepolymerization step, to the preformed prepolymer and/or to the polymerization medium. The external electron donor may optionally be premixed with the co-catalyst. The external electron donor is added in any amount sufficient to effect production of the desired polyethylene. It is preferred to incorporate the external electron donor in a molar ratio of external electron donor to transition metal component of the Ziegler-Natta catalyst ranging from about 0.01:1 to about 100:1. In a more preferred embodiment, the molar ratio of external electron donor to transition metal component ranges from about 0.1:1 to about 50:1.
In carrying out the polymerization process of the present invention, the halogenated hydrocarbon is added to the polymerization medium in any amount sufficient to effect production of the desired polyethylene. It is preferred to incorporate the halogenated hydrocarbon in a molar ratio of halogenated hydrocarbon to transition metal component of the Ziegler-Natta catalyst ranging from about 0.01:1 to about 100:1. In a more preferred embodiment, the molar ratio of halogenated hydrocarbon to transition metal component ranges from about 0.001:1 to about 1:1.
The molecular weight of the polyethylene produced by the present invention can be controlled in any known manner, for example, by using hydrogen. The molecular weight control may be evidenced by an increase in the melt index (I2) of the polymer when the molar ratio of hydrogen to ethylene in the polymerization medium is increased.
The molecular weight distribution of the polyethylene produced by the present invention is expressed by the melt flow ratio (MFR). Preferably, the polyethylenes have MFR values varying from about 24 to about 34, and densities ranging from about 0.880 gm/cc to about 0.964 gm/cc.
The polyethylenes of the present invention may be fabricated into films by any technique known in the art. For example, films may be produced by the well known cast film, blown film and extrusion coating techniques.
Further, the polyethylenes may be fabricated into other articles of manufacture, such as molded articles, by any of the well known techniques.
The invention will be more readily understood by reference to the following examples. There are, of course, many other forms of this invention which will become obvious to one skilled in the art, once the invention has been fully disclosed, and it will accordingly be recognized that these examples are given for the purpose of illustration only, and are not to be construed as limiting the scope of this invention in any way.